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Unit 4, Lesson 9
Keeping You and Your Computer Safe
AOIT Computer Systems
Copyright © 2008–2013 National Academy Foundation. All rights reserved.
Working with computers is relatively safe
• Take precautions to minimize risk.
• Understand and follow safety procedures.
• Monitors and power supplies are the most hazardous devices.
Electrostatic discharge (ESD) can be shocking
• ESD is the rapid flow of static electricity from one object to another.
• Energy is released in the form of a spark.
• ESD is costly and dangerous.
• ESD can interrupt power to a system.
Protect yourself from ESD
• Don’t become a conductor of electricity.
• Damage to components can occur at low voltages.
Can you remember a time when you felt an electric shock? What do you think caused it?
Ground yourself for safety’s sake
• Ground is neutral:• Not positively or negatively charged with
electricity• Connected to the earth
• Grounding creates:• An easy path for electrical current to follow• The same electrical potential between two objects
• The best sources for ground:• AC outlet • Metal chassis of a PC that is connected
to a known ground
What do you think this universal symbol for ground is based on?
Safety Ground
Wear an antistatic wrist strap
• Ground yourself by wearing an antistatic wrist strap.
• Attach the clip to a good ground source.
• Never try to repair monitors or power supplies. Opening a monitor, especially while wearing an antistatic wrist strap, could release a lethal charge of electricity.
Why do you think an antistatic wrist strap would make a monitor or power supply release a charge of electricity?
Antistatic mats slow the flow of static electricity
• Antistatic mats use electrical resistance to slow the flow of static electricity across the surface of the mat.
• Be sure the mat is grounded.• Use antistatic spray on the floor around the work area.
Three-layered antistatic mats reduce ESD.
Power supplies retain a dangerous charge
• The power supply is extremely dangerous.
• Even when unplugged, the capacitor retains a potentially lethal electrical charge.
• A power supply is a field replaceable unit (FRU):
• There are no serviceable parts inside.
• Replace a failed unit with a new one.
You can minimize the risk of ESD damage
• Store and ship computer components in antistatic bags.
• Wear an antistatic wrist strap when handling components.
• Remove components from the bag slowly.
• Maintain humidity levels between 70% and 90%.
• Never touch the electrical contacts on components.
Damage from electro-magnetic interference (EMI) is recoverable
Common sources of EMI:
• High-speed digital circuits
• Radio transmitters
• Power line intercoms
• Electric motors
• Fluorescent lights
• Network cabling too close to other devices
• Electric space heaters
Always follow best practices for safety
• A computer’s safety documentation contains more information: • Setup precautions• Safe cleaning instructions• Fire hazards during usage • Electrocution hazards
during usage
• Refer to the documentation for electrical specifications.